Lignin resins and process of making same



Patented Mar. 28, 1950 LIGNIN RESINS Raymond Norris Evans lrassia, Laurel, Miss Corporation, Laurel,

Delaware No Drawing. Application May AND PROCESS OF MAKING saw:

and Angelo Paul Inassignors to Masonite Miss., a corporation of Serial No. 672,156 7 6 Claims. (Cl. 260-473) This invention relates to resins having high resistancetoalkaliandwaterandmadefrom components comprising lisnin in substantial proportioneandthemethod ofmakingandusins such resins.

By the present invention. lignin, which is readily soluble in alkali, forming dark-colored soluticns,isreactedwithanaminotriazine andan aldehyde, whu'eby resin is obtained which is resistant to alkali. resistant to absorption of water, and has therm characteristics. In order to secure intimate admixture of the reactive componenm and so facilitate their reaction, they maybeintimatelymixedinthedrystateina conventional mixing apparatus, or they may be put into solution in organic solvents adapted to dissolve the reactive components.

The reaction between lignin. an aminoia'iazine and an aldehyde can be carried out with use of an alkali soluble lignin which has been isolated, or itcanbecarriedoutwithsuchlignininsitu in acid-hydrolysed iigno-cellulose iiber, or both. In carrying on the reaction with lisnin in acid-hydrolyned llgno-cellulose fiber, hardboards, molded products and the like, containing such fiber as wellastheresinousproductsofthereactioncan be produced which are resistant to alkali and water.

The main objects of the invention are the provision of resins made fl'om lisnin. an aminotriazine and an aldehyde. and of products containing such rains and acid-hydrolyzed iigno-cellulose fiber, which resins and products are of high alkali resistance, and are resistant to absorption of water, and the provision of methods for the production of such resins and resin containing products.

In carrying out the present invention, lignin is caused to react with an aminotriazine, preferably melamine, and an aldehyde, preferably formaldehyde or paraformaldehyde, at an elevated temperature. If desired, the melamine and formaldehyde may be reacted to form a condensation prbduct (one of such condensation products is sold under the trade-name "Melmac 402) before addition to and reaction with the lignin to form the novel nin resins.

The relative proportions of the reactants may vary within fairly wide limits. lihrcellent results have been obtained with proportions ranging from 1 up to about 6 moles of formaldehyde, preferably about 3 moles formaldehyde, to 1 mole of melamine. The proportion of lignin may be from about 10% up to about 80%, preferably about 30% to 40%, based upon the weight the melamine.

The soluble lignin used in the reaction in mierably provided by subjecting wood or other lianocellulose material to hydrolysis in the presence of mild acids. The acid-hydrolysed limo-cellulose material is preferably P pared by subjecting wood chips to the action of high-pressure steam in a'closed chamber, as for example a gun, as described in U. S. patent to Mason No. 1.824.221. In such treatment, organic acids such as acetic and formic acids are formed, and acid'hydrolysis of the liens-cellulose material is effected, with lignin being set free. After treatment with steam, the contents of the gun are disintegrated, preferably by being explosively discharged from the resion of high steam pressme to a resion of substantially atmospheric pressure. Material so produced has a. pH of about 3 to 4.

The time required for the steam treatment decreases rapidly with increase of the steam pressure used. For example, 25 minutes treatment with steam at 2'75 p. s. 1. (temperature of 212' C.) has approximately the same eifect as treatment for 5 seconds with steam at 1000 p. s. i. (temperature of 285 C.) Such treatment is well adapted for production or fiber for making hardboards and like products.

In general, the longer the steam treatment is continued at a given temperature, the higher is the proportion of the freed soluble lisnin. and such longer steam treatment is preferable in case the lignin is to be extracted. For example. fiber obtained from wood chips subjected to steam raised to 600 p. s. i. in 30 seconds, then raised to 1000 p. s. i. and held for 5 seconds. followed by preferab y explosive disintegration, contains a good proportion of extractible lignin. as for example 10 to 12% or dry weight of chips. Higher yields of such lignin can be extracted from lignocellulose material given a steam treatment of 15 or more seconds with steam at 1000 p. s. 1., for example. For illustration, a typical figure for yield oi solub'e lienin from wood ch ps treated with steam at 1000 p. s. i. for 15 seconds and reduced to fiber is about 17-18% based on dry weight of chips. The steam-treated and disintegrated material is preferably washed with water to largely remove the water-soluble organic acids, such as formic and acetic, and water-soluble derivatives of hemi-celiuloslc material.

For extraction of the lignin from acid-hydrolyzed Ilene-cellulose, dilute alkali solution, such as 1-3% sodium hydroxide solution for ex mp e, is pre erably used. and the lignin precipitated by acidification of the solutio as for example by addition of hydrochloric acid, and then separated filtration. The separated lignin is preferably heated with dilute hydrochloric acid to set free any cations picked up in the process, iiltered and washed with distilled water. Instead of treating with dilute alkali. organic solvents, such as methyl "Cellosoive" for example, can be used to dissolve the iignin. and the lignin recovered by precipitating in water or by evaporating the solvent or in other ways. Treating the entire mass of hydrolyzed ligno-ceilulose with such organic solvents is expensive and it is preferred to extract the lignin therefrom with dilute alkali solution and precipitate it and then confine the treatment with the organic solvents to the lignin material so obtained. The lignin used for resin making in examples below was prepared by treatment of acid-hydrolyzed exploded wood fiber with 3% sodium hydroxide solution at a temperature of 50" 0.. and treated with dilute hydrochloric acid and washed as above described. Such lignin when precipitated and dried is light and fiuify.

Acid hydrolyzed ligno cellulose fiber for making sheet or like products is prepared. for example, by subjecting wood or other lignoceliulose material to the action of high pressure steam, as described above. The hydrolysis treatment of the limo-cellulose material is. howout at a less degree of severity as compared with the degree of hydrolysis applied to ligno-cellnlose material which from the liquid by is hydrolyzed for the purpose of extracting lignin therefrom. The less severe hydrolysis is a plied in preparation of the fiber stock in order to retain a better degree of fiber structure. The acidhydrolyzed ligno-cellulose fiber thus prepared contains about 5 to 12% lignin (based on the weight of the ligno-cellulose material) freed as a result of the hydrolysis. This lignin contained in the ligno-cellulose material will readily react with the melamine and formaldehyde components. If desired, additional lignin may be added with the melamine and formaldehyde components, to increase the amount of lignin resin in the final reaction product, and such additional lignin may or may not have been previously reacted with the melamine and the formaldehyde.

since the reaction is preferably carried out in the presence of acid-hydrolyzed ligno-cellulose fiber, no catalyst need ordinarily be added because of the acidic nature of the ligno-cellulose fiber. If catalysts are added they should preferably be acid catalysts. such as for example, phthalic acid. maleic acid. or the like. Ordinarily no added catalysts are necessary. but they may be used if desired to carry out the reaction at specially low temperatures.

The reaction between lignin, melamine and formaldehyde is conveniently carried out in the presence of oxygenated organic compounds in which the melamine with the formaldehyde and the lignin are soluble. Suitable organic compounds for this purpose are mono alkyl ethers of ethylene glycol, such as methyl Cellosolve" and ethyl Cellosolve, dioxane, tetrahydrofuri'uryl alcohol and the like, or mixture thereof. such organic compounds may or may not enter into the reaction.

The melamine, formaldehyde and llgnin may also be reacted without adding a solvent, as for example. with the use of parai'ormaldehyde. In such cases the lignin. melamine and paraformaldehyde are thoroughly dry mixed followed by the application of heat and pressure to the mixed components.

Although melamine and formaldehyde are the preferred components for reaction with lignin, other triazines and aldehydes may be used to form lignin-resin products. Other triazine compounds which may be used include melamine derivatives such as 2,4,6 trlethyltriamino-1,3,5 triazine, 2.4.6 triphenyltriamlno-l.3,5 trinzine and the like, ammeline, ammeiide, formoguanamine and the like. Other aidehydes which may be used are. for example, acetaldehyde. furfural, benzaldehyde, and the like or mixtures thereof.

Parts in the examples which follow are parts by weight.

Example 1.-l parts of melamine. 3'75 parts of 37% formaldehyde solution. 54 parts of lignin and 106 parts of methyl Cellosolve" (monomethyl ether of ethylene glycol) were placed in a flask, and the mixture heated and stirred 15 hours at a temperature of 45' C. The resin produced was a black thick liquid resin which became viscous on standing for 48 hours at room temperature.

Acid-hydrolyzed ligno-cellulose fiber material was repared by subjecting hardwood chips to the action of steam in a closed chamber at a pressure raised to 600 p. s. i. and corresponding temperature in about 30 and then raised to 1000 p. s. i. with temperature. The last named pressure was held for about 4 seconds and the treatment with steam was followed by disruptiveiy discharging the chamber contents to substantially atmospheric pressure. The fiber contained about 12% of free lignin. which was freed as a result of the hydrolysis treatment of the ligno-cellulose material. The fiber was ground and through a ail-mesh screen.

parts of the above prepared resin were mixed with 265 parts methyl 0ellosolve" together with 100 parts of the above prepared acidhydrolyzed ligno-celluloee fiber. After thorough mixing of the components in a mechanical mixer, theresiniibermixturewasplacedinawire basket and air-dried at 50 C. until the volatile content was reduced to about 15%. The material was ground and through a iii-mesh screen. The volatile contents were further reduced to about 5% by heating in an oven.

A molded specimen of the ground material was prepared by pressing the material for a period oi'5minutesinaheatedpressatapressureof 1750 p. s. i. and temperature of 0., and chilling while under The molded specimen had the following Example 2. parts of melamine and 3'15 parts of 37% formaldehyde solution were stirred at65C.for3hours. To130partsofthethus formed melamine and formaldehyde reaction product was added 12 parts of lignin and the realization continued with stirring to produce a res To 100 parts of acidflbenpteparedasdescrlbedin Example Lwcre added 126 part 01' the above resin and 265 parts methyl "Cellosulve" and these materials thoroughly mixed in a mechanical mixer. This resin-fiber material was placed in a wire basket and held at a temperature 01' 70 C. in a vacuum oven for 5 hoursLand then dried at 50 C. for 15 hours until the volatile contents were reduced to about A molded specimen of the ground material was prepared by the material for a period of 5 minutes in a heated press at a pressure or 1750 p. s. i. and temperature of 165 C. and chilling while under pressure. The molded specimen had the following properties: 1. Specific gravi 1.35 2. Modulus of rupture (p. s. i.) 8,850 3. Hardness Rockwell M (room temp L... 102 4. Hardness Rockwell M 105 C 70 5. Water immersion 24 hours, per cent uptake 2.3 6. 1% alkali immersion 24 hours, per cent 11 2.4 7. Color of alkali solution Clear Example 3.-A resin solution was made by addl'ng 212 parts of methyl Cellosolve to 150 parts of a condensation product of melamine and formaldehyde (sold in commerce as Melmac No. 402). To this solution .3 part of diammonium hycatalyst was added.

propel-hes:

1. Specific gravi 1.40 Modulus of rupture (p. s i) 13,040 3. Hardness Rockwell MI (room temp 104 4. Hardness Rockwell M 105 C '75 5. Water immersion 24 hours, per cent uptake 1.4 6. 1% alkali immersion 24 hours, per cent uptake 1.3 7. Color of alkali solutlom Clear Example 4.The following ingredients were weighed out and thoroughly mixed in a tubular minim-3 hours:

15 parts of melamine 4.5 parts lignin 10.7 parts paraformaldehyde 1.5 parts finely-divided alpha cellulose A portion of the multing mixture was pressed for 5 minutes in a mold at a pressure of 1750 p. s. i. and temperature of 130 C., and then chilled under The molded specimen had the follow ing 1. Specific grav1ty 1.44 2. m n Rockwell M (room temp.) 90 3. Rockwell M 105' C.- 4

8 4.1%alkal1 mmu-slonI4houmpe1-eent Ptake 1.4 5. Color of alkali eclutionJlery slightly dllcolcred press at a pressure or 1750 p. s. i. at a temperature of 165 C. and then chilling while unde pressure. The molded specimen had the following properties:

1. Specific gravity 1.40 2. Modulus of rupture (p. s. L)- 13,050 3. Hardness Rockwell M (room temp.) 106 4. Hardness Rockwell M 105 C '16 5. Water immersion 24 hours, per cent uptake 1.3 6. 1% alkali immersion 24 horns, per cent uptake 1.8 '7. Color of solution Clear Example 6.126 parts melamine, 288 parts furfural, 240 parts 01' 37% neutralized formaldehyde,

and parts lignin were of the formed resin solution, parts acid-hydrolyzed ligno-cellulose fiber and 200 parts methyl "Cellosolve" were placed in a Baker Perkins mixer and thoroughly mixed. The mixed fibrous mass was heated for about 20 minutes at 130 C. to substantially reduce the volatile content. The volatile content after such heating was about 10%.

Ai'ter grinding the fibrous mass and it through a 40-mesh screen, a molded specimen of the ground material was prepared by the material for a period of 5 minutes in a heated press at a pressure of 1750 p. s. i. and at a temperature of C. and chilling while under pressure. The molded specimen had the following properties:

The resins of the present invention can be wt to many uses in addition to those nessalsoadaptthemtorusein accuses board products. Also, their property or withstanding relatively high temperatures during the pressing operations specially adapts them for use as molding powders with or without suitable fillers in making hot molded products. Buch products, in addition to being good construction materials. are well adapted for iorm liners, drain boards. table tops and the like.

It is to be understood that the examples are for illustration only and not for limitation, and the breadth oi the invention is as defined in the claims.

We claim:

1. Process of preparing a theme-setting resin having water and alkali resistant properties which comprises dissolving alkali soluble lignin in an ether compound containing only C. H and 0, adding an amino-triazine compound having at least one hydrogen attached to the non-ring amino nitrogen and formaldehyde to the iignin solution, and subjecting the solution to heat to obtain a reaction between the lignin, the aminotriazine compound and formaldehyde.

2. Process of preparing a water and alkali resistant fibrous product which comprises subjecting a solution of melamine, formaldehyde, alkali soluble lignin and an ether compound containing only C, H and to heat to obtain a resinous reaction material, mixing the resinous reaction material with acid-hydrolyzed ligno-cellulose fiber material containing iree lignin, and heating the components to react the resinous reaction material with the lignin of the fiber material.

3. Process of preparing a water and alkali resistant fibrous product which comprises subjecting a solution of melamine, iormaldehyde, alkali soluble lignin and an ether compound containing only C. H and O to heat to obtain a resinous reaction material, mixing the resinous reaction material with acid-hydrolyzed lignocellulose fiber material containing free lignin, heating the mixture to remove a substantial proportion of volatile contents. and subjecting the mixture to heat and pressure to form a consolidated product.

4. Process of preparing a water and alkali resistant fibrous product, which comprises mixing alkali soluble lignin, melamine, paraiormaldehyde and cellulosic fiber, and subjecting the mixture to heat and pressure to form a consolidated product.

5. Process of preparing a water and alkali resistant fibrous product, which comprises mixing acid-hydrolyzed ligno-cellulose fiber. melamine and paratormaldehyde, and subjecting the mixture to heat and pressure to form a consolidated Product.

6. Process of preparing a water and alkali resistant product which comprises mixing a solution containing melamine and formaldehyde dissolved in an ether compound containing only C, H and O with hydrolyzed ligno-cellulose fiber, heating the mixture to substantially reduce the volatile content, and subjecting the mixture to heat and pressure to form a consolidated product.

RAYMOND NORRIS EVANS. ANGEDO PAUL INGRASSIA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,922,690 Lougovoy Aug. 15, 1933 2,068,926 Nevin Jan. 26, 1937 2,156,160 Olson Apr. 25, 1939 2,197,357 Widmer Apr. 16, 1940 2,197,724 Hovey Apr. 16, 1940 2,320,817 DAleiio June 1, 1943 2,368,451 D'Alelio Jan. 30, 1945 FOREIGN PATENTS Number Country Date 282,635 Great Britain Dec. 6, i928 

1. PROCESS OF PREPARING A THERMO-SETTING RESIN HAVING WATER AND ALKALI RESISTANT PROPERTIES WHICH COMPRISES DISSOLVING ALKALI SOLUBLE LIGNIN IN AN ETHER COMPOUND CONTAINING ONLY C, H AND O, ADING AN AMINO-TRIAZINE COMPOUND HAVING AT LEAST ONE HYDROGEN ATTACHED TO THE NON-RING AMINO NITROGEN AND FORMALDEHYDE TO THE LIGNIN SOLUTION, AND SUBJECTING THE SOLUTION TO HEAT TO OBTAIN A REACTION BETWEEN THE LIGNIN, THE AMINOTRIAZINE COMPOUND AND FORMALDEHYDE. 